Search PubMed⌕ Search

Biomedical subjects

Douglas F Stickle

Publications and source records attributed to Douglas F Stickle.

10 recordsLinked to original sources
PubMed2006

Predicted effects of hemoglobin A1c assay precision on a patient population distribution of serial hemoglobin A1c difference values.

BACKGROUND: Interpretation of serial measurements of % hemoglobin A1c includes an assessment of differences from preceding values (DHbA1c). We examined predicted effects of different assay precisions on an observed population distribution for DHbA1c. METHODS: Primary data were 5260 DHbA1c values from sequential HbA1c measurement pairs obtained within 1 calendar year. Each DHbA1c was replaced by a distribution obtained from sampling each component HbA1c value according to a normal distribution characterized by a fixed coefficient of variation (CV) of either 1%, 3% or 5% (forming data sets A, B and C, respectively). Data sets B and C, with inferior precision, were compared with the reference data set A (highest precision). RESULTS: Using DHbA1c bin widths of 0.5% HbA1c, differences in assay precision caused significant redistribution of numbers within bins. For instance, for CV=5%, there was a 7.2% decrease in the number of results within the DHbA1c bin=(-0.5 to 0.5. CONCLUSION: Different HbA1c assay CVs can significantly affect the fraction of patients within different clinical categorizations for DHbA1c and consequently may differently influence patient care recommendations.

Female↗
PubMed2006

Validation of use of annular once-punched filter paper bloodspot samples for repeat lead testing.

BACKGROUND: Lack of a second sample often precludes the ability to perform repeat lead measurements on filter paper bloodspot samples. We investigated whether annular specimens remaining from once-punched filter paper bloodspot specimens could provide accurate Pb measurements when measurements were scaled for the remainder area relative to the original punch area. METHODS: 50 microl bloodspot specimens were prepared using Pb-spiked EDTA whole blood. After removal of 6 mm punches, bitmap images of the remainder specimens were obtained using a scanner. Image analysis was used to determine the bloodspot area of the remainder sample relative to the area of the original punch. Measurement of Pb for punches and for remainder specimens was performed by ICP-MS. RESULTS: Area-corrected Pb measurements for remainder samples were significantly higher than for the punches, by an average factor of 1.52+/-0.12 (p<0.05, n=28). The difference was due to a discontinuity (an increase) in the per-area Pb at the bloodspot perimeter. Area-corrected results for annular specimens that excluded the perimeter were identical to those of the punch. CONCLUSION: Area-corrected Pb measurement using annular once-punched bloodspot remainder specimens can accurately reproduce lead measurements obtained from the original punch when the bloodspot perimeter area is excluded.

Color↗
PubMed2006

Cation binding linked to a sequence-specific CAP-DNA interaction.

The equilibrium association constant observed for many DNA-protein interactions in vitro (K(obs)) is strongly dependent on the salt concentration of the reaction buffer ([MX]). This dependence is often used to estimate the number of ionic contacts between protein and DNA by assuming that release of cations from the DNA is the dominant involvement of ions in the binding reaction. With this assumption, the graph of logK(obs) versus log[MX] is predicted to have a constant slope proportional to the number of ions released from the DNA upon protein binding. However, experimental data often deviate from log-linearity at low salt concentrations. Here we show that for the sequence-specific interaction of CAP with its primary site in the lactose promoter, ionic stoichiometries depend strongly on cation identity and weakly on anion identity. This outcome is consistent with a simple linkage model in which cation binding by the protein accompanies its association with DNA. The order of ion affinities deduced from analysis of DNA binding is the same as that inferred from urea-denaturation experiments performed in the absence of DNA, suggesting that ion binding to free CAP contributes significantly to the ionic stoichiometry of DNA binding. In living cells, the coupling of ion-uptake and DNA binding mechanisms could reduce the sensitivity of gene-regulatory interactions to changes in environmental salt concentration.

Amino Acid Sequence↗
PubMed2004

Evaluation of an assay for serum 1,5-anhydroglucitol (GlycoMark) and determination of reference intervals on the Hitachi 917 analyzer.

BACKGROUND: 1,5-Anhydroglucitol (1,5-AG) is a glucose analogue, which is decreased in hyperglycemic individuals. We report the technical performance of an assay (GlycoMark) on a chemistry analyzer, evaluation of analyte stability and determination of reference intervals for 1,5-AG in a non-diabetic US population. METHODS: NCCLS protocols were followed to evaluate the reagent on a Hitachi 917 chemistry analyzer. RESULTS: Intra- and interassay imprecision ranged from 1.3% to 3.8% and 0.79% to 3.7%, respectively. The assay was linear to 110 microg/ml. Interference from triglyceride, hemoglobin and bilirubin was <10% to concentrations of 12.6 mmol/l, 12.1 and 911.4 micromol/l, respectively. Correlation coefficients between lot numbers on the Hitachi 917 and between analyses on the Hitachi 917 and the Hitachi 7170 analyzers were >0.99. The lowest limit of detection was 0.49 microg/ml (mean+/-2 S.D.). 1,5-AG was stable at 4 degrees C for 7 days, at 22 degrees C for 5 days, at -80 degrees C for 14 days and for three freeze-thaw cycles at -80 degrees C. The US reference intervals (nonparametric 2.5th-97.5th percentiles) were 10.2-33.8 microg/ml (males) and 5.9-31.8 microg/ml (females). CONCLUSIONS: The performance of the GlycoMark assay for the measurement of 1,5-AG was acceptable on the Hitachi 917 analyzer.

Adolescent↗
PubMed2003

Effects of sterilizing gamma irradiation on bloodspot newborn screening tests and whole blood cyclosporine and tacrolimus measurements.

Sterilizing irradiation of the US mail has been proposed as a method to prevent delivery of viable anthrax spores. Because newborn screening samples (bloodspots) and cyclosporine and tacrolimus specimens (whole blood) are delivered routinely through the mail, we studied whether sterilizing gamma irradiation could affect these test results. Specimens were exposed to 18 kGy gamma irradiation (100 hours x 18,000 rad/h), a "kill dose" for Bacillus pumilus spore strips. Irradiation had no significant effect on whole blood cyclosporine or tacrolimus results, but it had a degradative effect on bloodspot phenylalanine, hemoglobins, biotinidase, galactose-1-phosphate uridyltransferase, thyroxine, and thyrotropin. Such irradiation potentially could cause false-negative results for the detection of phenylketonuria and likely would lead to an increase in secondary testing for hemoglobin variants, but it is unlikely to lead to false-negative or false-positive results for the remaining newborn screening tests. These experiments cannot rule out possible greater effects by larger doses or other types of irradiation.

Anthrax↗
PubMed2003

Evaluation of urine specimen integrity in a public health STD screening program.

Detection of Chlamydia trachomatis and/or Neisseria gonorrhoeae infection in urine using molecular amplification assays has permitted institutions with limited medical facilities to offer testing for these sexually transmitted diseases (STDs). The Nebraska Public Health Laboratory (NPHL) investigated the validity of urine samples submitted for C trachomatis and/or N gonorrhoeae amplification after receiving a substantial number of clear specimens. Approximately 75% of all urine specimens submitted for STD testing to the NPHL were from correctional facilities. The falsification of urine specimens submitted for microbiology studies is not evaluated routinely, and this problem was previously undocumented. By using the criteria for specific gravity of 1.001 or less and a creatinine concentration of less than 5 mg/dL (442 mumol/L), approximately 8% of all specimens submitted during the study interval were determined to be inconsistent with urine. The microbiology laboratory should be aware of the possibility for specimen manipulation to identify facilities submitting falsified specimens, to initiate appropriate intervention, and to minimize false-negative reporting.

Chlamydia Infections↗
PubMed2002

Role of hydration in the binding of lac repressor to DNA.

The osmotic stress technique was used to measure changes in macromolecular hydration that accompany binding of wild-type Escherichia coli lactose (lac) repressor to its regulatory site (operator O1) in the lac promoter and its transfer from site O1 to nonspecific DNA. Binding at O1 is accompanied by the net release of 260 +/- 32 water molecules. If all are released from macromolecular surfaces, this result is consistent with a net reduction of solvent-accessible surface area of 2370 +/- 550 A. This area is only slightly smaller than the macromolecular interface calculated for a crystalline repressor dimer-O1 complex but is significantly smaller than that for the corresponding complex with the symmetrical optimized O(sym) operator. The transfer of repressor from site O1 to nonspecific DNA is accompanied by the net uptake of 93 +/- 10 water molecules. Together these results imply that formation of a nonspecific complex is accompanied by the net release of 165 +/- 43 water molecules. The enhanced stabilities of repressor-DNA complexes with increasing osmolality may contribute to the ability of Escherichia coli cells to tolerate dehydration and/or high external salt concentrations.

Acetamides↗